Vehicle braking/driving force control device

Abstract

An ECU calculates the thermal margins of the in-wheel motors, on the basis of the thermal capacities of the in-wheel motors, the allowable limit temperatures, and the motor temperatures. Next, the ECU distributes the total requested torque between the requested torques for each wheel using the percentages of the thermal margins. The ECU controls the operation of an inverter such that the in-wheel motors generate the requested torques for the wheels. Thus, the four in-wheel motors generate uniform amounts of heat.

Description

TECHNICAL FIELD[0001]The present invention relates to a vehicle braking / driving force control device for controlling a driving force or a braking force to produce with each wheel of the vehicle individually.BACKGROUND ART[0002]As one form of electric cars, an in-wheel motor type vehicle in which a motor is arranged in or around the wheel placed under the vehicle body spring and drives the wheel directly is developed. In the in-wheel motor type vehicle, it is possible to control the driving force or the braking force given to each wheel independently depending on the traveling condition of the vehicle by an independent drive (power running) control or an independently regenerative control of a motor provided to every wheel.[0003]Because a motor is arranged in or around the wheel in such an in-wheel motor type vehicle, generated heat by the braking / driving movement of the motor is hard to be emitted and the motor is easy to be full of heat. Thus, for example, in the driving force cont...

AI Technical Summary

Benefits of technology

[0028]The driving force or the braking force of the wheel or the braking force should be distributed depending on the load balance between the front wheel and the rear wheel to obtain the good stability of the vehicle. However, because the cooling performance of in-wheel motors of all wheels decreases at the low-speed traveling, a difference is easy to be produced in the thermal margin of the in-wheel motor by adjusting the depending on the load balance. Thus, in the present invention, the distribution adjustment means lowers the degree to adjust to the distribution depending on the load balance when the vehicle speed is low in comparison with the case of high speed condition of the vehicle. That is to say, the degree to adjust to the distribution depending on the thermal margin balance is big when the vehicle speed is low in comparison with the case of high speed condition of the vehicle. Therefore, according to the present invention, at the normal traveling, the good stability of the vehicle is provided and can average the temperature of the each in-wheel motor at the low-speed traveling. Note that, the wording of “to acquire the load balance” means acquiring information representing the load balance. The load balance may be acquired, for example, from the detection value of a load sensor provided to detect the load acting on each wheel, or it may be acquired from the calculation value with the detection value of a vehicle height sensor and a spring constant of the suspension, or it may the preset fixed value.

Problems solved by technology

However, in the driving force control device proposed to Patent Literature 1, the distribution change of the braking / driving force responded to the heat generation state of the motor is not performed at all in the period when it is not estimated that motor temperature will exceed the permission limit temperature, and the braking / driving force of the motor is limited at the point in time when it is estimated that the motor temperature will exceed the permission limit temperature.

Therefore, during the period until the point in time, a big difference occurs in the use situation of each motor, and the heat generation state of each motor becomes imbalance, and a motor with enough thermal margins is mixed with a motor with a little thermal margins.

Thus, because thermal margins of each motor may become imbalance, only one motor may reach the permission limit temperature at an early stage.

In this case, because the braking / driving force of the motor will be limited from the point in time, the control property of the yaw rate or the lateral acceleration that can occur in the vehicle may decrease.

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